A forward-adjoint operator pair based on the elastic wave equation for use in transcranial photoacoustic computed tomography

Kenji Mitsuhashi, Joemini Poudel, Thomas P. Matthews, Alejandro Garcia-Uribe, Lihong V. Wang, Mark A. Anastasio

Research output: Contribution to journalArticlepeer-review


Photoacoustic computed tomography (PACT) is an emerging imaging modality that exploits optical contrast and ultrasonic detection principles to form images of the photoacoustically induced initial pressure distribution within tissue. The PACT reconstruction problem corresponds to an inverse source problem in which the initial pressure distribution is recovered from measurements of the radiated wavefield. A major challenge in transcranial PACT brain imaging is compensation for aberrations in the measured data due to the presence of the skull. Ultrasonic waves undergo absorption, scattering, and longitudinal-to-shear wave mode conversion as they propagate through the skull. To properly account for these effects, a wave-equation-based inversion method should be employed that can model the heterogeneous elastic properties of the skull. In this work, a forward model based on a finite-difference time-domain discretization of the three-dimensional elastic wave equation is established and a procedure for computing the corresponding adjoint of the forward operator is presented. Massively parallel implementations of these operators employing multiple graphics processing units are also developed. The developed numerical framework is validated and investigated in computer-simulation and experimental phantom studies whose designs are motivated by transcranial PACT applications.

Original languageEnglish (US)
Pages (from-to)2022-2048
Number of pages27
JournalSIAM Journal on Imaging Sciences
Issue number4
StatePublished - 2017
Externally publishedYes


  • Elastic wave equation
  • Image reconstruction
  • Photoacoustic computed tomography
  • Transcranial imaging

ASJC Scopus subject areas

  • Mathematics(all)
  • Applied Mathematics


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